How to add a custom trend line in WinForms Chart?

C#

//Assign the X and Y axes
this.chartControl1.PrimaryXAxis.ValueType = ChartValueType.DateTime;
this.chartControl1.PrimaryYAxis.ValueType = ChartValueType.Double;

//Configure the chart series
ChartSeries chartSeries = new ChartSeries("Sales");
foreach (var data in dataSource)
{
    chartSeries.Points.Add(data.Date, data.Sales);
}
chartSeries.Type = ChartSeriesType.Line;
this.chartControl1.Series.Add(chartSeries);

var trendLines = new[]
{
    new { Points = new[] { (new DateTime(2000, 1, 1), 10.0), (new DateTime(2002, 1, 1), 15.0) }, Color = Color.Red },
    new { Points = new[] { (new DateTime(2003, 1, 1), 20.0), (new DateTime(2005, 1, 1), 30.0) }, Color = Color.Green },
    new { Points = new[] { (new DateTime(2006, 1, 1), 35.0), (new DateTime(2008, 1, 1), 45.0) }, Color = Color.Red },
    new { Points = new[] { (new DateTime(2007, 1, 1), 20.0), (new DateTime(2010, 1, 1), 40.0) }, Color = Color.Green }
};

// Add all trend lines
foreach (var trend in trendLines)
{
    AddTrendLine(trend.Points, trend.Color);
}

void AddTrendLine((DateTime, double)[] points, Color color)
{
    ChartSeries trendSeries = new ChartSeries();
    trendSeries.Type = ChartSeriesType.Line;
    foreach (var point in points)
    {
        trendSeries.Points.Add(point.Item1, point.Item2);
    }
    trendSeries.Style.Interior = new Syncfusion.Drawing.BrushInfo(color);
    chartControl1.Series.Add(trendSeries);
}

VB

'Assign the X And Y axes
columnChart.PrimaryXAxis.ValueType = ChartValueType.DateTime
columnChart.PrimaryYAxis.ValueType = ChartValueType.Double

'Configure the chart series
For Each item In viewModel.PlantDetails
        ChartSeries1.Points.Add(item.Date, item.YValue)
Next
ChartSeries1.Type = ChartSeriesType.Line
columnChart.Series.Add(ChartSeries1)

Dim trendLines = {
    (Points:={(New DateTime(2000, 1, 1), 10.0), (New DateTime(2002, 1, 1), 15.0)}, Color:=Color.Red),
    (Points:={(New DateTime(2003, 1, 1), 20.0), (New DateTime(2005, 1, 1), 30.0)}, Color:=Color.Green),
    (Points:={(New DateTime(2006, 1, 1), 35.0), (New DateTime(2008, 1, 1), 45.0)}, Color:=Color.Red),
    (Points:={(New DateTime(2007, 1, 1), 20.0), (New DateTime(2010, 1, 1), 40.0)}, Color:=Color.Green)
}

' Add all trend lines
For Each trend In trendLines
Dim trendSeries = New ChartSeries()
trendSeries.Type = ChartSeriesType.Line
trendSeries.Style.Interior = New Syncfusion.Drawing.BrushInfo(trend.Color)
trendSeries.Style.Border.Width = 2
    For Each pt In trend.Points
          trendSeries.Points.Add(pt.Item1, pt.Item2)
     Next
     columnChart.Series.Add(trendSeries)
Next